It is known commonly as colon irrigation, and it is only performed by licensed professionals.  But essentially speaking, it has been used to detoxify the body, prevent disease supposedly, and achieve the general wellbeing you are looking for by ridding the body of toxins and even parasites.  There are various methods of colon cleansing in general.  But colon irrigation is more invasive than some.  Essentially speaking, they stick a tube up the rectum, after which they shoot water into the colon to cleanse it out.  It is rather high powered and can definitely get the parasites out, that then drain back through the original tube into a bucket below.  You can therefore even see what has been lying in your colon for yourself.  They generally do these in sessions, each session providing greater results and greater weight loss due to the loss of toxins. 

However, there have been some who have suggested that colon irrigation may actually damage the colon due to the idea that the water used in the process is too harsh and too high powered.  This may have some validity to it as the body is a complex, yet somewhat delicate machine and requires a certain amount of care.  Either way, it is one of the more invasive methods not often preferred by most individuals.